Oxy-Fuel Firing Reduces Circulation

As scale melts and runs off the steel surface, it exposes more virgin iron to the rapid oxidation (ablative melting). The exothermic heat release makes the reaction almost self-sustaining, similar to the reaction accomplished by a cutting torch. 

With burners that do not direct the combustion gases at the steel surface, the oxidation of the iron takes place without the velocity stimulant, so less oxygen contacts the hot surface. Without as much oxygen available, the reaction slows, and the exothermic heat of the reaction is not available to sustain the washing—similar to the effect of shutting off the oxygen to a cutting torch. 

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